The processes responsible for the association between divorce and adjustment in adults and their offspring are not well understood. The higher rates of behavioral and psychological problems in adults and children from divorced families were originally considered to be consequences of marital disruption, but may also reflect nonrandom selection of families into divorce. In order to disentangle these processes, the proposed research will utilize data from a longitudinal study of Australian adult twins and their offspring. First, analyses of monozygotic and dizygotic adult twins discordant for divorce will examine how genetic and environmental processes account for the increased problems among divorced individuals. Second, the children of twins design will investigate the causal and selection factors responsible for the relation between marital dissolution and functioning in young-adult offspring. Third, the proposed analyses will assess how family and individual characteristics mediate the environmental and genetic influences associated with offspring's adjustment to their parents' divorce. Finally, training opportunities will provide the opportunity to explore whether the family environment controls genetic expression of offspring behavior problems, use longitudinal data to study developmental changes in children's response to family conflict, and employ decision tree analyses to study how multiple risk and protective factors interact to influence child development. The proposed research seeks to move beyond simple associations between familial characteristics and outcomes and elucidate causal mechanisms by utilizing genetically informative designs, longitudinal data, and advanced quantitative methods.